Mdadm is the modern tool most Linux distributions use these days to manage software RAID arrays.
You should be able to use any block storage devices in a RAID. Any standard directions for setting up a RAID using SATA HDD’s should be applicable when using USB storage as well. You’ll have to set it up so that the USB devices are assembled as members of the RAID array.
Example
sudo mdadm --create --verbose /dev/md0 --level=1 /dev/sda1 /dev/sdb1
Change the devices to the ones used by the USB storage devices. Then assemble the array:
sudo mdadm --assemble --scan sudo mdadm --assemble /dev/md0 /dev/sda1 /dev/sdb1
Verifying the status of the RAID arrays
Checking the status/health of a RAID (also useful for checking a RAID is rebluilding):
cat /proc/mdstat
or
mdadm --detail /dev/md0
Create a new RAID array
Create (mdadm –create) is used to create a new array:
mdadm --create --verbose /dev/md0 --level=1 /dev/sda1 /dev/sdb2
If you get “mdadm: no raid-devices specified” try adding the raid-devices option
mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb2
sudo mke2fs /dev/md0
Remove a disk from an array
We can’t remove a disk directly from the array, unless it is failed, so we first have to fail it (unless it already is):
Fail sda1
mdadm --fail /dev/md0 /dev/sda1
Remove sda1 from array
mdadm --remove /dev/md0 /dev/sda1
Add a disk to an existing array
Normally done when replacing a failed disk:
mdadm --add /dev/md0 /dev/sdb1
Stop and delete a RAID array
If we want to completely remove a raid array we have to stop if first and then remove it:
mdadm --stop /dev/md0
mdadm --remove /dev/md0
Remove Superblock
mdadm --zero-superblock /dev/sda